(a) Field of the Invention
The present invention relates to a scheduling method and apparatus of a multi-antenna communication system, and more particularly, to a method and an apparatus for feeding-back a channel quality indicator (CQI).
(b) Description of the Related Art
In a cellular mobile communication system, the quality of a propagation channel varies depending on the position and the speed of a terminal. A base station and the terminal perform transmission and reception through a control channel and a traffic channel every transmission time interval (TTI) with a modulation order and a code rate suitable for the quality of the propagation channel.
To this end, the terminal feeds back a channel quality indicator (CQI) to the base station by referring to a reference signal transmitted for the purpose of estimating the propagation channel by the base station. Even in single user multiple-input multiple-output (SU-MIMO) communication used to increase a peak user rate of the terminal or multi user MIMO (MU-MIMO) communication for expanding a sector throughput, the CQI is fed back as a parameter for adaptively transmitting a plurality of data streams.
In a long term evolution (LTE) standard of 3rd generation partnership project (3GPP), 16 CQI levels which are fed back by the terminal are defined. Each CQI level is mapped to a modulation coding scheme (MCS) level for demodulation or decoding of each communication apparatus. Each MCS level is mapped to a specific signal-to-interference plus noise ratio (SINR).
Meanwhile, in recent years, for 5th generation (5G) mobile communication, a mobile communication method using a millimeterwave (mmWave) band has been researched. In the millimeterwave band, since a path attenuation increases as compared with a low frequency band, a transmission and reception beamforming technology is primarily used. In the millimeterwave band, more antennas than a frequency band of 2nd generation (2G) mobile communication can be used due to a relatively smaller wavelength. As a result, in the millimeterwave band, many streams can be simultaneously transmitted. As the number of simultaneously transmitted streams increases, interference applied among the streams can increase. In particular, since a CQI feed-back scheme of LTE MU-MIMO cannot accurately estimate an interference amount of paired streams, MU-MIMO performance can significantly deteriorate. Accordingly, for a smooth operation of the MU-MIMO, the CQI fed back by the terminal needs to be newly defined unlike the existing LTE.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.